Quick answer

A failed QuickBooks network diagnostic means the Database Server Manager scan could not confirm a working multi-user path between the server and its workstations. The failure falls into one of five areas: connectivity, hosting, firewall, file sharing or permissions. Fix the service and hosting layer first, then firewall, then share and folder rights, and run the scan again after each change.

What the QuickBooks network diagnostic actually tests

The network diagnostic runs inside QuickBooks Database Server Manager. You reach it from the QuickBooks Tool Hub: open the Network Issues tab on the server and select QuickBooks Database Server Manager, then scan your company-file folder from the Scan Folders tab. The scan checks that the database service responds, that hosting is active, that firewall permissions are in place, and that the shared folder is reachable.

When a check fails, the scan stops with a Network Diagnostics: Failed message and asks you to resolve the errors and retry. The message does not say which layer broke, so read the symptom that comes with it — a stopped service, a blocked ping, a permission error — and match it to the categories below.

This is the same diagnostic that reports "not running on this computer" service messages during a scan. It runs during the official H202 repair flow, so if workstations cannot enter multi-user mode, read this alongside the H202 fix order.

Failure categories and the exact fix path

CategoryWhat failedFix path
ConnectivityThe server cannot be reached — ping fails by name and IP, or the workstation is on another subnet or VPNStep 7
HostingHosting is off on the server, or a workstation is hosting in alternate modeStep 3
ServiceQuickBooksDBXX or QBCFMonitorService is stopped or crashingStep 2
FirewallThe dynamic QuickBooks port or a program is blocked by Windows Firewall or antivirusStep 4
File sharingNetwork discovery or file and printer sharing is off, or the folder is not shared over SMBStep 5
PermissionsQBDataServiceUserXX lacks Full Control of the folder or the shareStep 6

Symptoms that come with the failure

  • The scan finishes and reports Network Diagnostics: Failed with a prompt to retry.
  • A service message appears during the scan, such as QBCFMonitorService not running on this computer, even when the service shows as running in services.msc.
  • Workstations receive H202, H505 or a connection-lost error when they switch to multi-user mode.
  • The scan succeeds on the server, but workstations still cannot open the company file.
  • The failure returns every time the server restarts, especially on virtual machines that sleep.

Common causes, ranked

  1. Version mismatch. Database Server Manager and QuickBooks Desktop are different years, so the scan looks for the wrong service and fails.
  2. The database or monitor service is stopped. Either one being down fails the diagnostic.
  3. Hosting is off or duplicated. Only the server should host multi-user access; a workstation that hosts in alternate mode takes over the file.
  4. Firewall ports changed. QuickBooks 2019 and later use a dynamic port that can change after an update, and the old rule no longer matches.
  5. File sharing is disabled. Updates and security tools sometimes turn off network discovery or file and printer sharing.
  6. Share permissions are missing. The folder may be shared without giving the QuickBooks data service account access.
  7. Network isolation. A VPN, VLAN, second router or wireless client isolation separates the server from its workstations.

Before you begin

Run the diagnostic and repairs on the server, not a workstation. You need administrator rights, the QuickBooks admin password for File Doctor, and about thirty minutes. Record the exact failure message before you change anything; it is the fastest clue to the broken category.

Back up and warn your users first. Copy the entire company-file folder to another computer before you change services, firewall rules or permissions. Restarting the database service or switching hosting disconnects every open session, so work outside business hours.

How to fix a failed QuickBooks network diagnostic

1

Update the Tool Hub and match your Database Server Manager version

Download the current QuickBooks Tool Hub from Intuit and install it on the server. In services.msc, check the name of the QuickBooks database service: the number after QuickBooksDB is the QuickBooks year plus ten, so QuickBooks 2023 uses QuickBooksDB33 and QuickBooks 2024 uses QuickBooksDB34. If several versions are installed, the diagnostic can target the wrong one.

When you maintain more than one QuickBooks year, Intuit's install order is oldest first, newest last. The Database Server Manager reference covers reinstalling the component without touching QuickBooks.

2

Repair the database and monitor services

In services.msc, open QuickBooksDBXX. Set Startup type to Automatic, start the service if it is stopped, and open the Recovery tab. Set Restart the Service for first, second and subsequent failures. Repeat the same steps for QBCFMonitorService.

One quirk: the diagnostic briefly stops and restarts the monitor service while it runs, so a scan can report QBCFMonitorService not running on this computer even when the service is healthy. Watch the service status during the scan before you reinstall anything.

3

Turn hosting on, on the server only

On the server, open QuickBooks, go to File → Utilities, and select Host Multi-User Access if it is available. If the menu shows Stop Hosting Multi-User Access, hosting is already on. You can do this before opening a company file.

Then open File → Utilities on every workstation and select Stop Hosting Multi-User Access where it appears. A workstation left in alternate hosting mode owns the file and causes both this failure and H-series errors. The hosting mode guide explains how to spot a stray host.

4

Clear the firewall block

Open Database Server Manager and select Start Scan on the company-file folder. A successful scan resets firewall permissions automatically, which is often all the diagnostic needs. If the failure repeats, open the Port Monitor tab and note the current port for your version: 2019 and later use TCP 8019 plus a dynamic port, 2018 uses 8019, 56728 and 55378–55382, and 2017 uses 8019, 56727 and 55373–55377.

Create matching inbound and outbound rules in Windows Firewall, and allow QBW32.exe, QBDBMgrN.exe, QBServerUtilityMgr.exe, QBCFMonitorService.exe and QBUpdate.exe. After renewing a port, rescan the folder so the permissions reset. The firewall and ports guide lists every port and program path.

5

Restore file sharing and network discovery

On the server, open Network and Sharing Center → Change advanced sharing settings and turn on Network discovery and File and printer sharing. Then right-click the company-file folder, open Properties → Sharing, and confirm the folder is actually shared and reachable as \\server-name\share-name.

Keep the company file in a scanned local folder. The tool cannot monitor mapped drives, so a file on a mapped drive or NAS keeps failing the scan. Intuit's supported network list excludes NAS devices and virtual machines for this reason.

6

Correct folder and share permissions

Right-click the company-file folder, open Properties → Security → Advanced, select QBDataServiceUserXX and confirm it has Full Control. The XX matches your version — QuickBooks 2019 uses QBDataServiceUser29. Then open the Sharing tab and give the same account Full Control of the share.

On Windows Home editions the Security tab may be hidden; restart in Safe Mode to reach it. If the account is missing, turn hosting off and on so QuickBooks recreates it, then rescan.

7

Repair connectivity and name resolution

From a workstation, run ping server-name, then ping the server's IP address. If the IP replies but the name does not, fix name resolution with a static IP or DHCP reservation on the server, corrected DNS, or a temporary entry in the workstation's hosts file. If neither replies, check the subnet: the first three octets of both IPv4 addresses must match.

VPN tunnels, VLANs and wireless client isolation block the connection even when every QuickBooks setting is correct. Intuit lists VPNs and WANs as unsupported for Desktop multi-user work. Keep both machines on the same LAN segment, and confirm the multi-user network setup matches Intuit's recommended layout.

8

Re-run the diagnostic and retry the scan

Restart the server, open the Tool Hub, and run QuickBooks Database Server Manager from the Network Issues tab. Scan the company-file folder again and watch for the failure message. If the scan completes and lists your company files, open QuickBooks on a workstation and switch to multi-user mode.

If a single failure category keeps returning, run QuickBooks File Doctor from the Tool Hub's Company File Issues tab and choose Check your file and network. File Doctor works alongside the diagnostic and catches data-side problems that look like network failures.

Verify the fix

  1. Confirm the scan finishes without a network diagnostics failure and lists the company folder under QuickBooks company files found.
  2. Check that QuickBooksDBXX and QBCFMonitorService both show Running with Automatic startup.
  3. Open the company file from one workstation and confirm multi-user mode is active.
  4. Open the same file from a second workstation and post a test invoice, then delete it.
  5. Press F2 on the server to confirm the file name and local server information are correct.

If the network diagnostic still fails

Reboot the server and every workstation, then rerun the scan before making more changes. A clean restart clears locked sessions and starts the services in the right order.

If the failure follows a Windows update, reinstall the Database Server Manager component and rescan. If it appears only when a specific workstation is online, that machine is likely hosting in alternate mode or running endpoint security that interferes with SMB traffic. When workstations still drop, review multi-user not working and engage an IT professional; Intuit support does not troubleshoot third-party VPN, VLAN or NAS setups.

Prevention

  • Keep QuickBooks Desktop and Database Server Manager on the same version year and update both together.
  • Leave the database and monitor services on Automatic startup with automatic recovery enabled.
  • Rescan the company-file folder after moving the file, renewing a port or installing a Windows update.
  • Keep the company file on a local drive on the server — not a mapped drive, sync folder, NAS or VPN share.

Frequently asked questions

Why does the diagnostic say QBCFMonitorService is not running when it is?

The scan stops and restarts the monitor service as part of its checks, so it can read the status during that gap and report a false failure. Open services.msc and watch the service while the scan runs. If it stays Running after the scan, the message is a side effect, not the cause of the failure.

Should I run the network diagnostic on the server or a workstation?

Always on the server, the computer that stores the company file and runs Database Server Manager. The Tool Hub's Network Issues tab expects to run there. Running it on a workstation gives incomplete results because the workstation does not host the database service.

Does a failed diagnostic mean my company file is damaged?

Usually not. The diagnostic tests the connection path, not the accounting data. A failure normally points at a service, hosting, firewall, sharing or permissions problem. If the scan passes but QuickBooks still reports data errors, run Verify and Rebuild instead.

Can I use QuickBooks multi-user mode over a VPN?

Intuit lists VPNs among the network types it does not recommend or support for QuickBooks Desktop, because the encrypted tunnel often blocks the database connection. For remote access, use a supported remote desktop or hosting arrangement instead.

Sources & further reading